Integrated circuit package with molded insulation

ABSTRACT

A variety of improved arrangements and processes for packaging integrated circuits are described. More particularly, methods of encapsulating dice in lead frame based IC packages are described that facilitate covering some portions of the bottom surface of the lead frame while leaving other portions of the bottom surface of the lead frame exposed. In some embodiments, a method of encapsulating integrated circuits mounted on a lead frame panel is described. The lead frame panel includes a plurality of leads having associated contacts and supports. A shim having a plurality of cavities is positioned under the lead frame such that the cavities are adjacent to the supports and not adjacent to the contacts. During the encapsulation process, encapsulant material flows under the supports such that the bottom surfaces of the supports are electrically insulated by the encapsulant while the bottom surfaces of the contacts remain exposed.

CROSS REFERENCE TO RELATED APPLICATIONS

The following application is a Divisional of U.S. patent applicationSer. No. 11/614,281 entitled INTEGRATED CIRCUIT PACKAGE WITH MOLDEDINSULATION, filed on Dec. 21, 2006, which is herein incorporated in itsentirety by reference.

BRIEF DESCRIPTION OF THE INVENTION

The present invention generally relates to the packaging of integratedcircuits (ICs). More particularly, methods of encapsulating dice in leadframe based IC packages are described that facilitate covering someportions of the bottom surface of the lead frame while leaving otherportions of the bottom surface of the lead frame exposed.

BACKGROUND OF THE INVENTION

There are a number of conventional processes for packaging integratedcircuits. Many packaging techniques use a lead frame that has beenstamped or etched from a metal (typically copper) sheet to provideelectrical interconnects to external devices. One relatively recentlydeveloped package style is a micro-array package. A lead frame suitablefor use in a micro-array style package includes a plurality of leads.Generally, each lead includes a contact post and the leads are etched,half-etched, or otherwise thinned relative to the contact posts. A dieis electrically connected to the thinned portions of the leads viabonding wires. Generally, the die, lead frame and bonding wires are thenencapsulated while leaving the bottom surfaces of the contact postsexposed to facilitate electrical connection to external devices.

Given their many advantages, micro-array packages have recentlygenerated a great deal of interest within the semiconductor industry.Although existing micro-array lead frame based packaging techniques workwell, there are continuing efforts to develop even more efficientdesigns and methods for packaging integrated circuits using micro-arraylead frame technology.

SUMMARY OF THE INVENTION

A variety of improved arrangements and processes for packagingintegrated circuits are described. More particularly, methods ofencapsulating dice in lead frame based IC packages are described thatfacilitate covering some portions of the bottom surface of the leadframe while leaving other portions of the bottom surface of the leadframe exposed. Several embodiments of the invention are discussed below.

In one method aspect of the invention, a shim and a populated lead framepanel are positioned in a mold. The lead frame panel has a tape adheredto its bottom surface. The shim has a plurality of cavities. The shimand lead frame panel are arranged such that first portions of the leadframe panel that contact the tape are positioned adjacent selected shimcavities and second portions of the lead frame panel that contact thetape are not positioned adjacent any shim cavities. An encapsulant isinjected into the mold to encapsulate dice mounted on the lead framepanel. Some of the encapsulant material displaces the tape in regionswithin the cavities such that encapsulant material flows under the firstportions of the lead frame panel. At the same time, the tapesubstantially prevents encapsulant material from flowing under thesecond portions of the lead frame panel.

The described arrangement can be used in the formation of a wide varietyof lead frame based packages. By way of example, in micro-array typepackages, the described arrangement can be used to electrically insulateportions of the lead frame (such as support posts) that aresubstantially co-planar with the microarray contact pads.

In a separate aspect of the invention, an improved micro-array leadframe panel is described. In this aspect, the micro-array lead framepanel includes a plurality of device areas, each device area having anarray of contact posts. Each contact post is integrally formed from anassociated lead segment. The bottom surfaces of the lead segments arerecessed relative to the bottom surface of the lead frame panel whilethe bottom surfaces of the contact posts are substantially coplanar withthe bottom surface of the lead frame panel. Additionally, each devicearea of the micro-array lead frame panel includes a plurality ofelongated support segments located peripherally around the array ofcontact posts. Each elongated support segment is also integrally formedwith an associated lead segment and is suitable for use in supportingthe associated lead segment during wire bonding or other process steps.

In a separate aspect of the invention, a shim suitable for use inencapsulating integrated circuit packages is described. In this aspect,the shim includes a plurality of shim device areas, each shim devicearea having one or more shim cavities. The shim cavities are arrangedsuch that when the shim is appropriately positioned adjacent to anassociated lead frame panel having a plurality of corresponding leadframe device areas, first portions of the lead frame device areas arepositioned adjacent to the shim cavities while second portions of thelead frame device areas are not positioned adjacent to any of the shimcavities.

In yet another aspect of the invention, an integrated circuit package isdescribed. The IC package includes a lead frame having an array ofcontact posts, a plurality of lead segments and a plurality of supportslocated peripherally of the array of contact posts. Each contact postand support is integrally formed with an associated lead segment. Thebottom surfaces of the lead segments are recessed relative to the bottomsurface of the lead frame while the bottom surfaces of the contact postsand supports are substantially coplanar with the bottom surface of thelead frame. The IC package also includes a die that is carried by andelectrically connected to the lead frame. The lead frame, die andelectrical connections are encapsulated such that the lead segments andsupports are not exposed at the bottom surface of the package while thebottom surfaces of the contact posts are exposed at the bottom surfaceof the package. In this way, the supports are electrically insulated bythe encapsulant while the contact posts remain exposed to facilitateelectrical connection to an external device.

Other aspects and advantages of the invention will become apparent fromthe following detailed description taken in conjunction with theaccompanying drawings, which illustrate, by way of example, theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, reference should be made tothe following detailed description taken in conjunction with theaccompanying drawings, in which:

FIG. 1A illustrates a diagrammatic top view of a lead frame panelsuitable for use in packaging integrated circuits in accordance with anembodiment of the present invention.

FIGS. 1B-1C illustrate successively more detailed views of selectedelements of the lead-frame panel of FIG. 1A.

FIG. 2A illustrates a diagrammatic top view of a shim suitable for usein conjunction with the lead frame panel of FIG. 1A in packagingintegrated circuits in accordance with an embodiment of the presentinvention.

FIGS. 2B-2C illustrate successively more detailed views of selectedelements of the shim of FIG. 2A.

FIGS. 3A-3B illustrate the lead frame panel of FIGS. 1B-1C overlaid onthe shim of FIGS. 2B-2C.

FIGS. 4A-4C illustrate diagrammatic cross-sections of the lead framepanel of FIG. 1A during various stages of packaging in accordance withan embodiment of the present invention.

FIGS. 5A-5B illustrate diagrammatic cross-sections of a lead inaccordance with an embodiment of the present invention.

FIGS. 6A-6B illustrate diagrammatic three-dimensional renditions ofleads in accordance with other embodiments of the present invention.

FIG. 7 illustrates a more detailed view of a portion of the lead framepanel of FIG. 4C highlighting the separation of the tape from portionsof the lead frame panel overlying the shim cavities duringencapsulation.

FIG. 8 illustrates a diagrammatic cross-section of a packaged IC formedin accordance with an embodiment of the present invention.

FIG. 9 is a flow chart illustrating a process for fabricating ICpackages in accordance with an embodiment of the present invention.

In the drawings, like reference numerals are sometimes used to designatelike structural elements. It should also be appreciated that thedepictions in the figures are diagrammatic and not to scale.

DETAILED DESCRIPTION OF THE DRAWINGS

The invention relates generally to the packaging of integrated circuits(ICs). More particularly, methods of encapsulating dice in lead framebased IC packages are described that facilitate covering some portionsof the bottom surface of the lead frame while leaving other portions ofthe bottom surface of the lead frame exposed.

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the present invention. Itwill be apparent, however, to one skilled in the art that the presentinvention may be practiced without some or all of these specificdetails. In other instances, well known process steps have not beendescribed in detail in order to avoid unnecessary obscuring of thepresent invention.

FIG. 1A illustrates a diagrammatic top view of a lead frame panelsuitable for use in packaging integrated circuits according toembodiments of the present invention. A lead frame panel 101 can beconfigured as a metallic (or other conductive) structure having a numberof two-dimensional arrays 103 of device areas 105. As illustrated in thesuccessively more detailed FIGS. 1B-C, each device area 105 of thetwo-dimensional array 103 is configured for use in a single IC package.Additionally, fine tie bars 107 connect the device areas to one anotherwithin the array 103. During packaging, one or more semiconductor diceare affixed to each device area 105, where they are then subjected towire bonding, encapsulation and singulation processes, yieldingindividual IC packages.

In order to facilitate these processes, each device area 105 has anumber of leads 111, each supported at one end by the tie bars 107.During die attach and wire bonding processes, dice are attached to theleadframe and bonding pads on the dice are electrically connected to theleads 111 via bonding wires or other suitable electrical connections.

There are applications, including many analog applications, thatnecessitate that selected leads carry more current than that which canbe reliably carried by a single bonding wire. In applications such asthese, two or more bonding wires may be required between a bonding padon the die and an associated lead on the lead frame. However, thebonding process may be sufficient in many instances to cause the leadsto bow or flex excessively, or even to fail.

To mitigate bowing of the leads, supports 115 extending to the bottomsurface of the lead frame 101 are positioned under the leads 111 inregions in proximity to where the bonding wires are bonded to the leads.By way of example, the supports 115 may take the form of support postsor elongated support segments. The supports 115 support the leads 111during wire bonding processes. However, as described in more detailbelow, the supports may increase the exposed metal surface area on thebottom surface of the package, which may increase the propensity forelectrical shorting. It is therefore desirable to electrically insulatethe supports 115.

In the embodiment illustrated in FIGS. 1A-C, selected leads 111 includecontact posts 113 and supports 115 integrally formed with the selectedleads 111. The leads 111 are etched, half-etched, or otherwise thinnedrelative to the contact posts 113 and supports 115. Each contact post113 extends to the bottom surface 419 of the lead frame panel 101 toprovide a conductive contact pad 417 at the bottom surface of the leadframe. This configuration is best illustrated in FIG. 4A whichillustrates a cross section A-A of FIG. 1C after the lead frame 101 hasalready been subjected to the die attach and wire bond processes, butprior to encapsulation. Each support 115 also extends to the bottomsurface 419 of the lead frame 101 to provide a support structure forselected leads 111. In this manner, only bottom surfaces of the contactposts 113 and supports 115 may be coplanar with the bottom surface 419of the lead frame panel 101. Additionally, as shown in the illustratedembodiment, the supports 115 are arranged peripherally around the deviceareas 105. It should be appreciated that, in various embodiments, it isnot necessary that all of the leads 111 include supports 115.

In various embodiments, the lead frame panel 101 may be configured suchthat each device area 105 includes a die attach pad or other die supportstructure 109. In one embodiment, the die attach pad 109 is integrallyformed with a plurality of contact posts. In this embodiment, the leadframe panel 101 may further include die attach pad support bars 117 thatconnect the die attach pads to the tie bars 107. The die attach padsupport bars 117 are also recessed relative to the bottom surface 419 ofthe lead frame panel 101 and may optionally include integral supports115.

The described lead frames are suitable for use in micro-array stylepackages, although the invention may be practiced with other lead framessuitable for use in alternative package styles. As will be explainedbelow, the devices may be encapsulated in a manner such that the contactpads 417 remain exposed at the bottom surface 419 of the encapsulatedlead frame panel 101 while the bottom surfaces 421 of the supports 115are not exposed at the bottom surface 419 of the encapsulated lead framepanel 101.

In some of the illustrated embodiments, the supports 115 havesubstantially circular cross-sections, as observed in FIG. 6A. However,it should be appreciated by those skilled in the art that the supports115 may assume a variety of shapes having varying cross-sectiongeometries. By way of example, the supports 115 may take the form ofcolumns having ovular or rectangular cross-sections. In a 11particularly preferred embodiment, each support 115 takes the form of anelongated support segment extending along a portion of an associatedlead 111. Additionally, the leads may be etched or thinned such thatfillets 533 are formed between the supports 115 and leads 111, contactposts 113 and leads, and/or the tie bars 107 and leads, as isillustrated in FIG. 5A. Representative fillets 533 may be observed inFIG. 5B, which illustrates cross-section B-B of FIG. 5A. Furthermore,the tie bars 107 may be etched such that integral ribs are formedbeneath the tie bars, which aid in reinforcing the tie bars whilereducing the amount of material that the dicing saws must saw throughduring singulation processes. In a similar fashion, the leads 111 may beetched or thinned so as to form ribs 106, as best observed in FIG. 6B,extending to the bottom surface of the lead frame panel 101. In thismanner, the ribs 106 serve as elongated support segments 115.Furthermore, the elongated support segments 115 may extend all of theway to the tie bars 107 such that the elongated support segments 115 areintegrally formed with the tie bars 107 (and when appropriate, the ribsof the tie bars).

FIG. 2A illustrates a diagrammatic top view of a shim suitable for usein packaging integrated circuits according to embodiments of the presentinvention. A shim panel 201 may be configured as a metallic structurewith a number of two dimensions arrays 203 of device areas 205. Asillustrated in the successively more detailed FIGS. 2B-C, each devicearea 205 of the two-dimensional array 203 is configured for use inencapsulating a single IC package. Each device area 205, as marked bythe dotted line 206 in FIG. 2C, includes one or more cavities 207. Invarious embodiments, adjacent device areas 205 may share a cavity 207,as is shown in FIG. 2C. Each cavity 207 may be in the form of a recessedregion formed by etching, half-etching, or otherwise processing aportion of the shim 201. By way of example, substantially rectangularcavities having depths of approximately 70 um have been shown to workwell. In alternate embodiments, cavities 207 may be in the form ofthrough-holes formed, by way of example, through etching, stamping, orotherwise processing portions of the shim 201.

During packaging, an adhesive tape 423 is attached to the bottom surfaceof the lead frame panel 101. Subsequently, one or more semiconductordice 425 are affixed to each device area 105, where they are thensubjected to known die attach and wire bonding processes. By way ofexample, bottom surfaces of the dice 425 may be adhesively attached todie attach pads 109 by means of a suitable die attach material or anadhesive tape. Bond pads on the dice may be electrically connected toassociated leads by conventional interconnect processes such as wirebonding. In some applications, it may be desirable to bond multiplewires 429 to a single lead 111. The supports 115 provide support for theleads such that the stresses of wire bonding operations do not cause theleads to flex or bow excessively, or otherwise fail.

To facilitate encapsulation, a shim 201 and a populated lead frame panelare placed in a molding cavity. As illustrated in FIGS. 3A-3C and 4B-4C,the lead frame panel 101 is placed on top of the shim such that thesupports 115 are laid over associated cavities 207 in the shim. In theillustrated embodiment, the two dimensional arrays 103 and 203, andcorresponding device areas 105 and 205 on the lead frame panel and shimhave substantially the same footprint such that the device areas 105 ofthe lead frame panel each overlay a corresponding shim device area 205.This is shown in FIGS. 3A-B, which illustrate a top view of the leadframe panel 101 laid over the shim 201. It should be noted that linescorresponding to the shim are dotted, but remain illustrated in FIGS.3A-3B, to indicate that the lead frame is placed over the shim. In theillustrated embodiment, the shim cavities 207 are sized and positionedsuch that two rows of supports 115 corresponding to two adjacent deviceareas 105 are placed over a single rectangular shim cavity 207, as bestseen in FIG. 3C. Thus, the shim cavity 207 underlies a segment of a tiebar and the supports 115 associated with the leads carried by the tiebar. However, it should be appreciated that the cavities 207 may bedesigned such that a lesser number of supports 115 may correspond to andbe placed adjacent a single shim cavity 207. It should also be notedthat in the illustrated embodiment, the shim cavities 207 do notunderlie the regions where the tie bars 107 intersect.

After the shim and lead frame panel have been placed in a mold, the leadframe panel may be encapsulated using conventional molding techniques.As will be appreciated by those familiar with the art, during molding,an encapsulant material is forced into the molding cavity at an elevatedtemperature and pressure. The pressure is sufficiently great that theliquid encapsulant displaces the tape 423 in regions over the cavities207. The displacement allows liquid encapsulant material to flow underthe support posts 115, as observed in FIG. 4C and FIG. 7, which is amagnified view of FIG. 4C. Once removed from the molding cavity, thetape 423 may be removed from the lead frame panel at any suitable time.In this manner, a layer of hardened encapsulant 431 is formed around thesupports 115 such that the bottom surfaces 421 of the supports are notexposed on the bottom surface of the encapsulated lead frame. By way ofexample, insulating layers of encapsulant having peak thicknesses in therange of approximately 50 to 100 _m are readily obtainable. By way ofexample, in some tests, insulating layers on the order of 68-70 _m havebeen formed and have been shown to work well. Such an insulating layerwas formed using cavities having a depth of approximately 70 _m and atape 423 having a thickness of approximately 35 _m.

It should be appreciated that since bottom surfaces 417 of the contactposts 113 are not adjacent the shim cavities 207 during encapsulation,the liquid encapsulant is unable to displace the tape in regions aroundthe contact posts, thus the bottom surfaces of the contact posts remainsubstantially uncovered by the encapsulant and exposed on the bottomsurface of the encapsulated lead frame.

When the cavities 207 are sized and positioned according to theembodiment illustrated in FIG. 3C, in which the cavities do not underliethe tie bar intersections, then regions where the tie bars 107 crosswill also remain substantially exposed on the bottom surface of the leadframe. Having visible tie bar intersections may be beneficial insingulation and inspection processes.

After the molding operation, the lead frame panel may be singulatedusing conventional singulation processes. Each resulting IC package 801includes a semiconductor die 425 that is attached to a lead frame devicearea 105. Of course, in some alternative embodiments, multiple dice maybe placed in each device area. The package 801 also has bonding wires429 that electrically connect the die 425 to the leads 111. Typically,the bonding wires are coupled to the leads in the vicinity of thesupports 115, although this is not always a requirement. An encapsulant431 surrounds the die 425 and lead frame 105, leaving only the contactpads 417 exposed at the bottom surface 833 of the IC package. Typically,electrical connectors (e.g., solder balls, solder paste, etc) areattached to the contact pads 417, although this is not a requirement.

It should be noted, that in practice, the shim may remain in the moldsuch that it may be used in encapsulating other lead frames.Additionally, in an alternate embodiment, the mold itself may beconfigured so as to have recessed cavities such that the shim isunnecessary. However, considering the great expense of molds and thatcustom molds would have to be developed for all package styles andconfigurations, in the interests of costs, versatility and reducingerror, it is desirable to produce relatively inexpensive custom shimsthat fit a general mold, rather than to produce custom molds.

Method of Fabrication

A method of fabricating IC packages in accordance with embodiments ofthe present invention is now described. FIG. 9 illustrates process stepstaken in the fabrication of such packages 801 as described earlier.

The process begins at 900 with applying an adhesive tape to the bottomsurface of a lead frame panel having a number of device areas, each ofwhich is suitable for use in an IC package. In one embodiment, each leadframe device area may be suitable for use in a micro-array style ICpackage. In such a micro-array style lead frame panel, each device areaincludes a plurality of leads. Selected leads include contacts that aresubstantially co-planar with the bottom surface of the lead frame panel,as well as a plurality of support posts (supports) that are alsosubstantially co-planar with the bottom surface of the lead frame panel.In this manner, both the bottom surfaces of the contact posts andsupport posts are in contact with the adhesive tape.

At 902, one or more dice are attached to the lead frame panel via knowndie attach techniques. The dice are then wire bonded to associatedbonding sites on the leads at 904. It should be noted that it isspecifically contemplated that multiple wires may be bonded to a singlelead. Such a need for multiple wires often arises in analog deviceapplications requiring greater current than which can be reliablycarried by a single wire.

The lead frame panel including the bonded dice is then laid in a moldover a shim at 906, such that the top surface of the shim is in contactwith the adhesive tape, which is, in turn, adhesively attached to thebottom surface of the lead frame. The shim includes a plurality ofcavities that are spaced and sized to correspond to designated firstportions of the lead frame, while designated second portions of the leadframe are not positioned adjacent to any shim cavities. In one preferredembodiment, the supports are among the first portions and the contactposts are among the second portions. The lead frame and shim are thensubjected to known encapsulation techniques such as injection molding at910. The encapsulant or molding material is forced into the mold usingconventional molding techniques. The pressure is sufficiently great thatthe liquid encapsulant displaces the tape in regions over the cavities,while not displacing the tape in regions over the land areas of the shim(i.e. in regions that are not adjacent the cavities). The displacementallows liquid encapsulant material to flow under the first portions ofthe lead frame (supports), while the tape and shim prevents theencapsulant from flowing under the second portions of the lead frame(contacts).

Once removed from the molding cavity, the tape may optionally be removedat step 912. In this manner, an insulating layer of hardened encapsulantis formed around the supports such that the supports are not exposed onthe bottom surface of the encapsulated lead frame. By way of example,insulating layers of encapsulant having peak thicknesses in the range ofapproximately 50 to 100 _m are readily obtainable. By way of example, insome tests, insulating layers on the order of 68-70 _m have been formedand have been shown to work well. Such an insulating layer was formedusing cavities having a depth of approximately 70 _m and a tape 423having a thickness of approximately 35 _m. Conversely, bottom surfacesof the contact posts, which are not positioned adjacent the shimcavities during encapsulation, remain uncovered by the encapsulant andexposed on the bottom surface of the encapsulated lead frame.

Once the lead frame is encapsulated, serial numbers or otheridentification numbers can be imprinted on the outer surface of theencapsulation material at step 914, and the solder balls or otherconnectors may be attached. If solder-based connectors are employed, anyoxidation may first be cleaned from the contact pads at 916. Thesurfaces of the contact pads are then treated appropriately, such as byapplication of Ni—Au plating if desired, or in some embodiments, simplecleaning with no other application of material to the pads. Solderconnectors may then be attached to the contact pads by known reflow orball attach processes at step 918. The individual packages can then besingulated at step 920, where they are then ready for inspection and/ortesting at step 922. It should be appreciated that some of theaforementioned steps can be implemented in a differing order. By way ofexample, the individual packages may be singulated prior to ball attach.The described method of electrically insulating the support posts hasbeen shown to eliminate shorting between support posts having a pitch ofless than 0.4 mm.

In an additional embodiment, a similar method may be used to createspacers on the bottom of an IC package. Spacers may be advantageous forpackages that necessitate that a space is maintained between the bottomsurface of the package and the top surface of the printed circuit boardor other substrate to which the package is attached. By way of example,spacers may be particularly useful for land grid array (LGA) packagesnot employing solder balls. Solder joint reliability, which is generallyimportant for LGA packages, generally improves with an increasingdistance between the bottom surface of the package and the top surfaceof the substrate. Thus, spacers may be used to achieve greater solderjoint reliability. The method is virtually identical to that describedabove. However, rather than positioning the shim cavities adjacent tosupports or other exposed portions of a lead frame or other conductivestructures, the shim cavities are placed wherever spacers are desired onthe bottom surface of a molded package. Such spacers can be formed inpackages that have conductive structures exposed on their bottom surfaceand in packages that do not have conductive structures exposed on theirbottom surface.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the invention.However, it will be apparent to one skilled in the art that the specificdetails are not required in order to practice the invention. Thus, theforegoing descriptions of specific embodiments of the present inventionare presented for purposes of illustration and description. They are notintended to be exhaustive or to limit the invention to the precise formsdisclosed. It will be apparent to one of ordinary skill in the art thatmany modifications and variations are possible in view of the aboveteachings.

In the illustrated embodiment, the cavities were rectangular and weresized such that each cavity could accommodate two entire rows of supportposts. However, based on the application and the desired layout of theleads, as well as the tolerances required, other cavity layouts, sizes,and shapes may prove beneficial. For example, the cavities may becircular in shape and each sized for a single support post.Alternatively, the cavities may be ovular in shape and sized for a rowof support posts. Edges of the cavities may also be beveled such thatthe tape is more easily deformed and more displacement is achieved.

The embodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, to therebyenable others skilled in the art to best utilize the invention andvarious embodiments with various modifications as are suited to theparticular use contemplated. It is intended that the scope of theinvention be defined by the following claims and their equivalents.

1. A lead frame panel suitable for use in semiconductor packaging, thelead frame panel comprising a matrix of tie bars that define a pluralityof device areas, each device area being configured suitably to supportan associated die and including: an array of contact posts, each contactpost having a contact pad that is substantially co-planar with a bottomsurface of the lead frame panel; a plurality of lead segments carried byassociated tie bars, each lead segment being integrally formed with anassociated contact post, wherein upper surfaces of the lead segments aresubstantially co-planar with an upper surface of the lead frame paneland bottom surfaces of the lead segments are recessed relative to thebottom surface of the lead frame panel, and wherein some of the leadsegments extend between contact posts associated with other leadsegments; and a plurality of elongated support segments locatedperipherally around the array of contact posts, each elongated supportsegment being integrally formed with an associated lead segment, whereinbottom surfaces of the elongated support segments are substantiallyco-planar with the bottom surface of the lead frame panel, and whereineach elongated support segment extends along a portion of an associatedlead segment but does not extend to an associated contact post such thateach elongated support segment is longer than it is wide.
 2. A leadframe panel as recited in claim 1, wherein the elongated supportsegments do not extend to the outermost periphery of their associateddevice areas.
 3. A lead frame panel as recited in claim 1, wherein theelongated support segments extend to the outermost periphery of theirassociated device areas.
 4. A lead frame panel as recited in claim 3,wherein the elongated support segments are integrally formed withassociated tie bars.
 5. A lead frame panel as recited in claim 1 whereineach device area further includes a die attach pad, the die attach padbeing integrally formed with a plurality of the contact posts.
 6. A leadframe panel as recited in claim 5 further comprising die attach padsupport bars that couple the die attach pads to associated tie bars, thedie attach support bars having upper surfaces that are substantiallyco-planar with the upper surface of the lead frame panel and bottomsurfaces that are recessed relative to the bottom surface of the leadframe panel.
 7. A lead frame panel as recited in claim 6 wherein atleast some of the die attach pad support bars are arranged as leadsegments that have associated elongated support segments.
 8. A leadframe panel as recited in claim 1 wherein the lead frame panel takes theform of a lead frame strip having a plurality of spaced aparttwo-dimensional arrays of device areas therein.
 9. A lead frame panel asrecited in claim 1, wherein the elongated support segments are thinnerthen portions of their associated lead segments above the elongatedsupport segments.
 10. A lead frame panel as recited in claim 9, whereinthe elongated support segments curve into their associated lead segmentssuch that fillets are formed at the intersections of the elongatedsupport segments and their associated lead segments.
 11. A shim suitablefor use in encapsulating integrated circuit packages, comprising: aplurality of shim device areas; and a matrix of shim cavities thatdefine the plurality of shim device areas, the shim cavities beingsuitably sized and positioned such that when the shim is appropriatelypositioned adjacent to an associated lead frame panel having a pluralityof lead frame device areas, first portions of the device areas of theassociated lead frame panel are positioned adjacent selected shimcavities and second portions of the device areas of the associated leadframe panel are not positioned adjacent any shim cavities; whereinduring encapsulation of the associated lead frame panel, the shimcavities facilitate covering the first portions of the device areas withencapsulant while the second portions of the device areas aresubstantially prevented from being covered with encapsulant.
 12. A shimas recited in claim 11, wherein the shim cavities are recessed regionsin the shim or through-holes in the shim.
 13. A shim as recited in claim11, wherein the lead frame panel takes the form of a lead frame striphaving a plurality of spaced apart two-dimensional arrays of deviceareas therein, and wherein the shim is configured to correspond to anassociated one of the plurality of spaced apart two-dimensional arraysof device areas.
 14. A shim as recited in claim 11, wherein the shimcavities are arranged peripherally around the shim device areas.
 15. Ashim as recited in claim 14, wherein adjacent shim device areas share ashim cavity.
 16. An integrated circuit package comprising: a lead framehaving an array of contact posts, a plurality of lead segments and aplurality of supports located peripherally of the array of contactposts, each contact post having a contact pad that is substantiallyco-planar with a bottom surface of the lead frame panel, each leadsegment being integrally formed with an associated contact post and eachsupport being integrally formed with an associated lead segment, whereinbottom surfaces of the supports are substantially co-planar with thecontact pads and wherein upper surfaces of the lead segments aresubstantially coplanar with an upper surface of the lead frame andbottom surfaces of the lead segments are recessed relative to the bottomsurface of the lead frame, and wherein some of the lead segments extendbetween contact posts associated with other lead segments; and a diecarried by the lead frame; a plurality of electrical conductors thatelectrically connect the die to selected lead segments; and anencapsulant that encapsulates the die, the electrical conductors and thelead segments such that the lead segments and supports are not exposedat the bottom surface of the package while the contact pads are exposedat the bottom surface of the package.
 17. A package as recited in claim16, wherein the supports are elongated support segments, wherein eachelongated support segment extends along a portion of an associated leadsegment but does not extend to an associated contact post such that eachelongated support segment is longer than it is wide.
 18. A package asrecited in claim 16 wherein the lead frame further includes a die attachpad, the die attach pad being integrally formed with a plurality of thecontact posts.
 19. A package as recited in claim 18 further comprising aplurality of die attach pad support bars having upper surfaces that aresubstantially co-planar with the upper surface of the lead frame andbottom surfaces that are recessed relative to the bottom surface of thelead frame, wherein the die is electrically connected to at least one ofthe die attach pad support bars and the contact posts associated withthe die attach pad may be arranged to be electrically active.
 20. Apackage as recited in claim 19 wherein at least one of the die attachpad support bars is arranged as a lead segment that has an associatedsupport.
 21. An integrated circuit package as recited in claim 16,wherein the electrical conductors that electrically connect the die toselected lead segments are bonding wires, and wherein at least twobonding wires are bonded to each of one or more selected leads havingsupports.
 22. An integrated circuit package, comprising: a lead framehaving an upper surface and a bottom surface, wherein the bottom surfaceof the lead frame includes a plurality of support surfaces that arecoplanar with the bottom surface of the lead frame and a plurality ofcontact surfaces that are substantially coplanar with the supportsurfaces; a die carried by the lead frame; a plurality of electricalconductors that electrically connect the die to selected portions of thelead frame; and an encapsulant that encapsulates the die, the electricalconductors and the lead frame such that the support surfaces are notexposed at the bottom surface of the package while the contact surfacesare exposed at the bottom surface of the package, wherein theencapsulant include protruding mounds that cover the support surfaces.